Telegraph line circuit



March 28, 1939. l K|NKEAD 2,151,772

TELEGRAPH LINE CIRCUIT Filed Oct. 14, 1936 i I QI 1 i i l i.

I 'E 'Qj j r m l l m I 2' LL: [F

INVENTOR A TTORNEV Patented Mar. 28, 1939 PATENT QFFIQE 2,151,772TELEGRAPH LINE cmoorr'.

Fullerton S. Kinkead, Ridgefield Park, N. J., assignor to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a, corporation of New York1 Application October 14, 1936, Serial No. 105,582

10 Claims.

This invention relates to improvements in long toll subscribers linesfor connection to teletypewriter exchanges and switching points. i

In furnishing service to subscribers it occa sionally happens thatcertain subscribers are too far from the nearest exchange or switchingpoint to be furnished service over a simple loop; an object of this.invention is to provide for such service with adequate provision forcalling and supervising connections with simple and efiective equipment.Such service may be furnished over line circuits operating on adifferential duplex, two-path polar or upset duplex basis. The system asdescribed herein will be a differential duplex system; the "principles.thereof can and have been applied to the other types of transmissionwith but slight changes in the circuit arrangements.

In the single figure of the drawing the linewith the line, circuitclosed through a ringer I l.

in the normally idle condition. The subscribers station also includes aswitch for turning on the power and closing the line, the usualteletypewriter sending contacts and receiving equipment of ateletypewriter,.a sending relay [5, and a break key. Further details'ofsuch subscribers circuits are disclosed in various pending United Statespatent applications but are not necessary here for a completeunderstanding of the invention.

The cord circuit for cooperating with the jack is may be of the typedisclosed in, the application of Locke and Kinkead, Serial No. 459,684,filed ;June 7, 1930, or patent to Kinkead et al. No.

2,624,581, granted December 17, 1935.

In transmission the subscribers line i3 terminates at repeater R, but inthe idle condition it terminates in relays "D and E of supervisoryequipment over back contacts of relays C and J.

The functions of the individual relays of the line equipment will now bedescribed.

, Relay B has one winding in the loop I! between the switchboard and therepeater R and the other is in a local biasing circuit and repeats allsignals to the relay F which is energized on a marking signal torelay B.

Relay F is ofthe slow release type; it holds operated on allteletype'writer signals but releases on break signals or openconditionsof the subscribers line. Y

subscriber station.

Relay 0 connects the line to the line side oi repeater R when energized,holds relay J operated and connects battery to the answering lamps AL.When reelased relay C connects the line l3 to contacts of relay J.

r Relay J, when operated, holds relay D oper ated and when releasedconnects the line l3 to windings of relays D and E. Relay J is slowrelease and during the release time it discharges the line throughresistance I660.

1 Relay D tests the line upon release of relay J to determine thestation condition and remains 1 operated when relay J releases if thecurrent from the subscribers station is positive (marking) or negative(spacing) but releases when the sub scribers station is idle. :Uponoperating relay D will close the lead to relay TL to light call lamp CLand to operate the night alarm (not shown) and upon release prepares aground path for operating relay A.

Relay E is not operated to close its contact when relay J is operatedbut is operated when marking potential is applied to the line.- at theOperation of relay E operates relay F.

Relay F operates relay 0; when relay F is operated it is held by relay0; relay F is slow release.

Relay H operates upon ringing current supplied from the cord over thetip of the jack and applies ringing current to line [3.

Relay G-is a sleeve relay and is operated from battery in the cordcircuit over the sleeve of jack IE; it opens the circuit to lamp AL andextends the communication circuit to jack it from winding of relay B.

' under the influence of its biasing winding.

Subscriber calls To call the subscriber applies positive potential tothe line. Relays D and E operate. Relay. D

V operates relay TL over back contact of relay G;

relay TL lights lamp CL. Relay E operates relay F, which operates relayC. Relay 0 connects negative battery to the windings of relays D and E.Polar relay E releases, relay D remains operated. Relay C connects linel3 to the line side of repeater R. Repeater R supplies a path forcurrent over lead I! to the operating winding of relay B from thepositive battery on lead l8.

Relay B closes its contact to hold relay F operated. Relay C alsoconnects battery to lamps AL and the winding of relay J. Relay Jtransfers the windings of relays D and E from negative battery overcontacts of relay C to apath through the back contact of the inner lowerarmature of relay A, also connected to negative battery.

The operator answers by inserting a cord in the line jack. Relay Goperates over the sleeve lead and disconnects lamp AL. Relay G alsoprepares the operating path of relay A and connects the communicationpath to the tip of the jack and cord. The ofiice side of repeater R isnow connected to the tip of jack I5 and the line side to the line 13over contacts of relays C and J. Relay B follows all teletypewritersspacing signals but relay F holds operated.

The subscribers station may now communicate with an operator on the cordcircuit (not shown) or thereover to another line.

Break signal from subscriber station A break signal holds relay B offits contact until relay F releases, which causes relay C to release.This opens the line 13 to the repeater which continues the spacingcondition. After release of relay C and before release of relay J theline is connected to resistance [6a and discharged. When relay Jreleases resistance |6a is disconnected from the line. Windings ofrelays D and E are transferred back to the line; as the station issupplying negative voltage to the line, relay D remains operated andpolar relay E remains released. At the end of the break positivepolarity is applied to the line. Relay E reoperates, relays F, C and Jreoperate, relay B closes its contact and communication may be resumed.

Break signal from cord circuit Upon a break signal from the cord circuitor beyond the relay B opens its contact; this releases relay E, whichreleases relays C and J. Relay J connects the operating path for relaysD and E to the line [3 but inasmuch as marking or positive polarity isapplied to the line by the subscriber during the break period, the relayE is operated, which in turn reoperates relays F, C and J. Uponreoperation relay J causes relay E to release by virtue of negativebattery supplied locally from the source on the back contact of thelower armature of relay C and front contact of relay J. If the breaksignal continues beyond this time this cyclic operation and reoperationmay continue as the relay F again releases upon release of relay E untilthe break condition is terminated to reoperate relay B, which reoperatesrelays F, C and J. Communication may then continue.

Disconnect signal from station to operator Consider now a disconnectsignal from the sub-'- scriber station. The attendant at the stationopens the line which releases relays B, F and C. Upon release of relay Cand during the holding time of relay J, the charge on the line will passto ground. Upon release of relay J, relay D will release and cause relayA to operate. Relay A, upon operating, opens the communication path,opens the path from battery to the upper armature of relay J, andconnects ground to the tip of the cord to operate a supervisory lamp inthe cord. The action of relay J in discharging the line is essential toprevent momentary operation of relay D which would interrupt the groundconnection to the tip of the cord and interrupt the lighting of thesupervisory lamp. The momentary operation of relay E is also preventedso that relay F will not be reoperated.

If the subscriber station disconnects during the time a break signal isbeing transmitted from the cord circuit, relay B will already have beenreleased and the release of relay E will cause the operation of relay Aand ground the tip lead when during the releasing and operating sequenceof the relays E, F, C and J as previously described the D and E relaysare next connected to the line.

The operator pulls down the cord and the circuit returns tonormal idlecondition.

Recall from the subscriber to the switchboard operator A recall signalis given by the station operator by operating a recall key which opensthe line to direct current for an interval and then recloses it. Uponopening the line relay D will release as described under the headingabove to operate the relay A and ground the tip of the cord. Uponreclosing the line the relay D reoperates and releases relay A whichremoves ground from the tip and causes the signal in the cord circuit tobe a recall or flashing signal (in a manner well known in the art anddescribed in the disclosures hereinabove mentioned).

A recall signal may be given to the switchboard operator during a breaksignal from the switchboard.

Calling the subscriber station Assume the station idle. The operatorplugs a cord plug into the jack i6. Relay G operates and because relay Dis released the relay A will operate. The ring of the jack and plug isgrounded. With the relay A operated the communication path will beopened at the upper armature. Alternating ringing current is appliedfrom the tip lead of the cord to the relay H over a circuit from the tipto the upper make contact of relay G, make contact of relay A and innerupper back contact of relay C. Upon operating the relay H causes relay Jto operate. released and relay A is operated no battery is supplied towindings of relays D and E by the contacts of relay J. Relays D and Eremain released during ringing. The upper contacts of relay H applyalternating ringing current to the line i3 over a make contact of relayH and a back contact of relay C. After each release of relay H theresistance l6a will discharge the line to prevent any false operation ofrelays D or E. When the station answers the relay B operates, relay Foperates, relay C operates and relay J operates; relay D operates andreleases relay A which connects the operating winding of relay B to thetip of the cord for communication in the same manner as when the stationcalled and the operator answered.

General With slight circuit modifications the principles of theinvention may be applied to two-path polar and upset duplex transmissionover the subscriber line. The necessary modifications are disclosed inthe copending application of Large and Locke, Serial No. 108,154, filedOctober 29, 1936. These modifications may be made a part of the presentcircuit by using the extra line conductor I3A, the extra armature andcontact on relay C, by closing switch l9 to contact 20 and switch 2| tocontact 22. The conductor l3, under this condition, transmits signals tothe subscriber's station Because relay D is and the conductor [3Areceives signals from the subscribers station which is disclosed indetail in the said application of Large and Locke.

The operating essentials of the subscriber station, so far assupervision is concerned, are first, that the two lines l3 and I3A inthe normal idle condition are connected together at the subscriberstation and connected through an alternating current ringer andcondenser to ground and that operation of the subscribers recall keyconnects the two lines together and isolates them from the transmissioncircuit at the subscriber station.

The operation is not different than described for differential duplexoperation. Note that when relay C is released the line receiving relayof repeater R is held to its spacing contact by negative batterysupplied over the switch I9 and the back contact of relay 0.

A general precaution in respect to this circuit is that relays D and Emust be made a bit sluggish or alternatively the contacts of relay Jmust be adjusted to operate in proper sequence, or both.

What is claimed is:

1. A subscribers telegraph toll line terminating circuit, a telegraphline therein normally terminating at a central oflice in relays, andrelays operated as a result of closing said line to shift thetermination to a telegraph repeater connected to means at said centraloffice conditioned for flexibly extending said circuit.

2. In a system for telegraphing and supervising exchange connectionsover a subscribers telegraph trunk line circuit, said circuit comprisinga local station, an incoming line and a repeater, a contact in said linebetween said station and repeater, a relay controlling said contact, anda slow release relay controlling said relay.

In a system for telegraphing and supervising exchange connections over asubscribers telegraph trunk line circuit, an incoming line, said lineincluding a repeater for repeating signals arriving thereover to a localconnecting circuit, said line being normally disassociated from saidrepeater and extending independently of said repeater through relaycontacts to elements controlling line operation signals.

4. In a system for telegraphing and supervising exchange connectionsover a subscribers telegraph trunk line circuit, an incoming line, saidline including a repeater for repeating signals arriving thereover to alocal connecting circuit, said line being normally disassociated fromsaid repeater and extending through relay contacts to elements, saidelements controlling line operation signals including a polar device anda nonpolar device.

5. In a system for telegraphing and supervising exchange connectionsover a subscribers telegraph trunk line circuit, an incoming line, saidline including a repeater for repeating signals arriving thereover to alocal connecting circuit,

said line being normally disassociated from said repeater and extendingthrough relay contacts to elements controlling line operation signals,and connections whereby said relay contacts are under'the control of arelay which is .actuable by said polar device to close said line to saidrepeater.

6. In a system for telegraphing and supervising exchange connectionsover a subscribers telegraph trunk line circuit, an incoming line, saidline including a repeater for repeating signals arriving thereover to alocal connecting circuit, said line being normally disassociated fromsaid repeater and extending through relay contacts to elementscontrolling line operation signals, and a polar device controlling saidrelay contacts to close said line through to said repeater, and devicesfor locking up said relay contacts under the control of said repeater.

7. In a system for telegraphing and supervising exchange connectionsover a subscribers telegraph trunk line circuit, an incoming line, saidline including a repeater for repeating signals arriving thereover to alocal connecting circuit, said line being normally disassociated fromsaid repeater and extending through relay contacts to elementscontrolling line operation signals, a

relay for transferring said line from said elements to said repeater, arelay locked up to maintain said transfer, means for releasing saidlocked up relay to restore said line to said elements, and means toconnect said line to ground for an instant prior to said restoration.

8. A subscribers telegraph toll line circuit, a repeater therein, a jackterminating saidline at a switchboard, a supervisory signal for saidline at the terminus including said jack, relay means at said terminus,means at a remote point upon said line for opening said line, means at aremote point for reversing the polarity upon said line, and a relay insaid relay means actuated to one position by opening said line and toanother posi tion by reversal of polarity thereof, and means wherebysaid signal is selectively actuated accordingly.

9. In a subscribers telegraph facility for connecting a subscriberspremises with a central telegraph switching oil'ice in a manualtelegraph switching system, said facility requiring a telegraph repeaterfor telegraph communication, the method for extending the distance rangeover which the subscriber has positive control over line operationsignals, between said subscriber and the central station operator, whichconsists in disassociating said repeater from the telegraph path whilesaid signals are being transmitted.

10. In a teletypewriter switching system, a subscribers station, acentral switching station, a telegraph path, normally open at saidsubscribers station, connecting said stations, a telegraph repeater,individual to said path, and means in said path for switching saidrepeater into said path.

FULLERTON S. KINKEAD.

